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Power grids

Just the FACTS

Developing countries across ASEAN, like Thailand, are hungry for electric power in both big cities and increasingly rural areas. Flexible AC Transmission Systems (FACTS) are perfectly suited to help increase the reliability of AC grids and reduce power delivery costs.

Picture the intense power needs in a place like the booming industrial sector in Vietnam, Dubai during the hot, summer months or growing cities like metropolitan Manila. By regulating voltage and stabilizing power generation systems FACTS can meet the growing need for power.
The idea is not new. The underlying FACTS concepts have been around for decades: they strive to improve transmission quality and efficiency by supplying inductive or reactive power to the grid via these solutions.

  • Series Compensation (SC)
  • Static Var Compensator (SVC), SVC PLUS
  • Synchronous Condenser Solution
  • Mechanically Switched Capacitors (MSC/MSCDN)


Siemens manufactures FACTS systems and has been successfully executing such projects around the world for decades. Its advanced system software and technical hardware (like cutting edge, Thyristor Controlled Series Capacitors (TCSC) and Thyristor Protected Series Capacitors (TPSC) technology) make them essential tools for power utilities striving for maximum grid performance. In fact, Siemens’ first Static Var Compensator (SVC) for a utility application using Tyristor Controlled Reactors (TCR) was commissioned in 1980.

In Thailand, Siemens is deploying parallel compensation systems like SVC to regulate voltage across networks experiencing extreme fluctuations, and series compensation systems, which increase the capacity of long distance transmission lines.

Stabilizing Thailand’s grid

The Electricity Generating Authority of Thailand (EGAT) is partnering with Siemens to ensure a reliable and flexible national grid. For EGAT, being the single buyer of bulk electricity within Thailand, FACTS technology allows for a stable grid. As part of a consortium, they are building two SVC units: Bang Saphan 2 (total capacity of 400MVAr in the range of +300MVAr capacitive and -100MVAr inductive power and the other at Phuket 3 Substation (total capacity of 150MVAr in the range of 100MVAr capacitive and 50MVAr inductive power). “They have done very well on this and I think most Siemens products have been widely accepted by most power utilities in the world,” said EGAT Deputy Governor Mr. Kijja Sripatthangkura.

To share power and maintain a stable grid while using traditional sources of power as well as Renewable Energy (RE), FACTS are imperative. “As we study Thailand’s power system, reactive compensation equipment such as SVC is important because reactive power can ensure constant power,” said EGAT’s Deputy Governor Sripatthangkura.

This FACTS technology will efficiently increase the power flow from Central to Southern Thailand, stabilize the growing power needs in Phuket, and mitigate voltage fluctuations and instability, which could cause blackouts. Siemens sees both SVCs as a perfect opportunity to enhance the power grid in Southern Thailand and also the ASEAN Grid Connection.

Step up and step down voltage

Siemen’s parallel compensation systems, such as SVC technology, fit particularly well in South-East-Asia where fast industrial growth can burden power distribution on ageing electrical grids – some of which were haphazardly constructed over decades. Additionally, modern policy and priorities are calling for power production from RE sources like solar, wind, gas etc. But these are often unreliable and make grids even more unstable and susceptible to outages, making the bespoke design of each SVC system essential. SVCs are used in two main situations:

  • Connect to the power system to regulate the transmission voltage ("Transmission SVC")
  • Connect near large industrial loads to improve power quality ("Industrial SVC")


The Transmission SVC is used to regulate the grid voltage. If the power system's reactive load is capacitive (leading), the SVC will use Thyristor-controlled reactors to consume VARs from the system, lowering the system voltage. During under-inductance (lagging), the capacitor banks are automatically switched on, providing higher system voltage. By connecting the Thyristor-controlled reactor along with a capacitor bank step, continuously regulation of variable leading or lagging power is achieved.
The Industrial SVC is usually put near high and rapidly varying loads, such as arc furnaces, where they can smooth flicker voltage.
 Some of the SVC control features include:

  • Voltage control
  • Reactive power control
  • Damping of power oscillations
  • Unbalance control


SVCs have the advantage over mechanically switched compensation of near instantaneous response to system voltage changes. SVCs are usually cheaper, higher capacity, faster and more reliable than dynamic compensation schemes such as synchronous condensers. But some static VAR compensators are more expensive than mechanically switched capacitors, so many systems use both: static VAR compensator for swift changes and mechanically switched capacitors for steady-state VARs.

Positioning Thailand for APG

While each ASEAN country is developing its own power grid, they’re also cooperating on a common ASEAN policy for power interconnection and trade, and ultimately the realization of the ASEAN Power Grid (APG) to help ensure greater regional energy security and sustainability. Because customers are demanding for Earth-friendly energy solutions, the use of (often unreliable) RE sources is becoming more common. Since Thailand is surrounded by four countries: Lao PDR, Cambodia, Myanmar, and Malaysia, FACTS also gives Thailand great potential to inter-connect the transmission systems.
Siemens deems SVCs as a perfect technology to enhance the power grid in Thailand and also to embrace the spirit of ASEAN: sharing value together, working together and planning for the ASEAN Power Grid.

Glenn van Zutphen is a journalist based in Singapore.
Picture credits: Hans Sautter